The magnetron of a microwave oven oscillates in the vicinity of a frequency of 2.45 GHz, and emits unwanted radiant waves to an ambient environment. For this reason, there is a problem in that the communication distance of a wireless communication device which performs wireless communication in that frequency band is extremely shortened due to the influence of unwanted radiation from the microwave oven, or the wireless communication device may not perform communication.
A wireless communication device for avoiding this problem has been proposed. The microwave oven operates with a commercial power supply (AC 100 V, 200 V, or the like), and the AC frequency of the commercial power supply is 50 Hz or 60 Hz. The voltage of the microwave oven periodically passes through the point of the voltage 0 V (zero cross point), and oscillation of the magnetron is temporarily stopped in the vicinity of the zero cross point. The wireless communication device of the related art detects this timing and performs wireless communication in synchronization with the zero cross point (for example, see PTLs 1 to 3).
However, the method of the related art has the following problems.
(1) When the wireless communication device is not connected to the commercial power supply, the zero cross point may not be detected by the wireless communication device to begin with.
(2) Even if the wireless communication device is connected to the commercial power supply, it is necessary to provide an additional circuit for detecting the zero cross point in the wireless communication device.
(3) If countermeasure communication (transmission aimed at the zero cross point) is performed, the effective transmission rate decreases. Accordingly, when the microwave oven is not in operation, it is preferable that countermeasure communication is not performed. However, in the method of the related art, since the operation state of the microwave oven may not be accurately recognized by the wireless communication device, countermeasure communication is constantly performed so as to remain unobstructed.
(4) When the microwave oven is in operation, even if countermeasure communication is not performed, communication may become successful depending on the conditions. However, in the method of the related art, countermeasure communication is performed without exception. The conditions include when the distance between wireless communication devices is short, the oscillation intensity of the magnetron is lowered by heat control of the microwave oven, when oscillation is temporarily stopped, and the like.
As described above, in the method of the related art, since communication is performed aimed at the timing of the zero cross point, there is a problem in that it is necessary to synchronize with the commercial power supply or it is necessary to accurately recognize the operation state of the microwave oven.    [PTL 1] Japanese Patent Unexamined Publication No. 2002-111603    [PTL 2] Japanese Patent Unexamined Publication No. 2002-319946    [PTL 3] Japanese Patent Unexamined Publication No. 2002-323222